Biofuel can be used both for central- and decentralized production of electricity and heat or as petrol replacement.
In one way biofuel is conserved by “capturing” energy from the sun through the process of photosynthesis in growing plants. However, generally, one advantage of biofuel in comparison to most other fuel types is that biofuel is biodegradable, and thus relatively harmless to the environment if spilled.
Biofuel was used in the early days of the car industry. In Germany the combustion engine was provided to run on ethanol and the diesel engine was initially made to run on peanut oil. However due to very cheap extraction of crude oil (crude mineral oil) the industry preferred to provide engines running on the cheaper extracts of crude mineral oils rather the more expensive biofuels.
Nevertheless, biofuel remained a slightly interesting combusting ingredient in particular in a blend with petrol or as a blend of gasoline with alcohol fermented from potatoes in some countries, such as Germany and Britain.
However, due to the increasing use of combustible fuels and at the same time avoid or limit the stress on the surrounding environment, alternative fuel-products which are relatively harmless to the environment, such as biofuels, have gained more attention. Hence, as of 2005, bioenergy, such as biofuel, covers approximately 15% of the world's energy consumption and the consumption is still increasing.
One problem of the presently available methods for producing biofuel is that the yield of biofuel obtained from the method is not high enough to keep a low price of the biofuel in order to make it competitive to conventionally used mineral oils.
Hence, it has been of interest to combine the production of biofuel with the production of alternative valuable by-products. One such product may be protein, which traditionally is isolated from the distillate after e.g. ethanol has been removed from the suspension, by distillation. The problem with this method is that the protein will denature during the high temperature treatment of the distillation process and the only applicability of the protein produced is as an animal supplement.
To overcome this problem, proteins were suggested separated from the suspension before distillation to obtain the ethanol. However, protein products obtained by this method showed to have a very high content of impurities because of unspecific methods used making them unsuitable for human consumption. Use of conventional chromatography, packed bed adsorption techniques, was suggested in order to provide more pure protein products, however, this showed to be undesirable because the production costs became much too high and the production time was also increased to an undesirable extent.
Hence, an improved method for producing biofuel and protein which has a high degree of productivity per unit cost, which is fast, which is reproducible, which requires a minimum of handling steps, which is specific in order to limit the extent of impurities in the protein product and which preferably be compatible with automated and semi-automated systems for optimising performances of the isolation of biofuel and the purification of protein product would be advantageous.